Combustion chambers for pistons



y 1962 s. MEURER 3,034,489

COMBUSTION CHAMBERS FOR PISTONS Original Filed June 9, 1958 INVENTOR Hjz'egffiz'ed Maura/ AiTORN d United States Patent 3,034,489 COMBUSTIONCHAMBERS FOR PI STONS Siegfried Meurer, Numberg, Germany, assignor toMaschinenfabrik Augsburg-Numberg A.G., Number-g,

This invention relates to combustion chambers for pistons. Inparticular, the invention is directed to cornbustion chambers forself-ignition engines.

This application is a division of my application Serial No. 740,08,filed June 9, 1958, for Combustion Chambers for Pistons, now Patent2,975,773, issued March 21, 1961.

The piston of this invention is designed to operate in self-ignitionengines such as disclosed in U.S. Eatent No. 2,907,308. In such engine,the liquid fuel is in ected into a hollow combustion chamber in thepiston. The injection is made in such a way that the major portionof thefuel travels over a short free path and is applied immediately to thewall of the combustion chamber. After striking the chamber wall, thefuel spreads out as a film over a part of the wall. The remaining minorportion of the fuel is atomized directly in the air in the chamber andis self-ignited for igniting the fuel vaporized from the film of fuel.Combustion air is swirled over the film of fuel to vaporize the same.

In these engines, it is desirable to have the fuel cover as much aspossible of the chamber wall. If the chamber, as in former pistons, isspherical or ellipsoidal and the fuel strikes the wall at a sharp angle,the fuel is spread as a film in a satisfactory manner. Because of thekinetic energy of the fuel, it has a tendency to spread peripherallyabout the wall of the combustion chamber. However, in these chambers,the spreading of the fuel is handicapped by the concave curve of thespherical or ellipsoidal chamber. Such chamber forms act in the natureof a groove with the fuel tending to flow along the bottom thereof andnot completely spread out.

The object of tlus invention is to produce a combustion chamber formedas a body of rotation and having a shape such that the fuel will spreadout evenly in all directions on the wall of the chamber.

In accordance with the invention, the combustion chamber is in the formof two oppositely directed conical chamber portions, with the twoportions connected at their bases. A chamber so constructed has beenfound to improve the cold starting of an engine. This is because of thesudden change given the direction of the spreading fuel over the jointbetween the two conical sections. The fuel at this point is momentarilydetached from the wall. Consequently, the air swirling across theseparated fuel atomizes the fuel which is of special advantage for highboiling point fuels. A similar effect can be obtained if the chamberwall and bottom are of spherical shapes with different curvatures. Inthe latter construction, as compared to the two conical portionconstruction, the momentary separation of the fuel from the film can beaccomplished closer to the opening into the combustion ice chamber sothat the atomization is more eifective in the starting of the engine.

When the combustion chamber is in the form of two conical portions,these conical portions can be symmetrical and axially aligned. However,in a modified construction, the conical portions can be eithernon-axially aligned, or can be axially out of line, or can benon-symmetrical for purposes of forming fuel films desirable for certaincombustion processes.

The means by which the objects of the invention are obtained aredescribed more fully with reference to the accompanying drawings, inwhich:

FIGURE 1 is a longitudinal cross-sectional view through a piston in acylinder with the piston having a combustion chamber according to thisinvention; and

FIGURES 2 and 3 are similar views of respective modified forms of thecombustion chamber.

As shown in FIGURE 1, the combustion chamber 1 is posit oned in thepiston head of piston 2, the chamber being coaxial with the axis ofpiston 2 and cylinder 3. A nozzle 4 is inclined in the cylinder head 4aabove the combustion chamber. The major portion of the injected fuel isapplied to the combustion chamber wall by several fuel jets 4b which aredirected at a sharp angle toward the wall and form a film thereon. Thisfilm is vaporized from the wall and mixed with the air swirling in thechamber to produce a combustible fuel mixture. The minor portion of thefuel it atomized immediately in the air swirling in the chamber. Thisatomizing is accomplished by either deflecting a part of the injectedfuel into the air or by a special ignition jet, not shown. As the fuelleaves the nozzle, it has a kinetic energy which moves the fuelcircumferentially around and upon the combustion chamber wall.

As shown in FIGURE 1, the combustion chamber 1 is connected to thesurface of the piston by means of a cylindrical neck 9 and is composedof two oppositely directed conical portions 12 and 14, respectively, inthe form of truncated cones with their bases joined on the line 16.Chamber 1 is coaxial with the longitudinal axis of the piston. Along theline 16, the wall of the chamber is interrupted to form an irregularsurface which causes the fuel being applied to be momentarily separatedfrom the chamber wall. This separated fuel mixes with the air swirl inthe chamber and thus causes an atomizing of at least a part of thisseparated fuel.

When it is desired to apply the fuel to particular wall areas, such canbe accomplished by the arrangement of the portions of the chamber wall.As shown in FIGURE 2, the conical portions 12a and 1411, instead ofbeing coaxial, are displaced with respect to each other as by having thetwo axes at an angle to each other. Alternatively, as shown in FIGURE 3,the conical portions 12b and 14b are made asymmetrical with respect toeach other.

Having now described the means by which the objects of the invention areobtained,

1 claim:

1. In a piston having a combustion chamber for receiving a film of fuelinjected upon the wall of the chamber, said fuel being then vaporizedand burned, the improvement comprising a downwardly directed combustionchamber extending from the top surface of the piston into the pistonbody, said chamber having wall surfaces in 3 a 4 the form of a pair ofoppositely extending truncated cones 6. In a piston as in claim 1,further comprising a cywith their larger bases joined to one another. xlindrical neck between the top surface of said piston and 2. In a pistonas in claim 1, said pair of truncated said combustion chamber; conesbeing symmetrical and coaxial.

3. In a piston as in claim 1, said pair of truncated cones 5 Referencessited in the file of s patent being non-coaxial.

v 4. In a piston as in claim 1, said pair of truncated cones UNITEDSTATES PATENTS being asymmetrical with respect to each other. 2,881,743Holt Apr. 14, 1959 5. In a piston as in claim 1, said pair of truncatedcones being non-coaxial and non-symmetrical with respect to 10 FOREIGNPATENTS each other. 1,207,557 France Sept. 7, 1959

